HIV is a chronic disease that demands unremitting adherence to medication. Interventions that support therapeutic adherence may therefore need to be unending as well. Unfortunately, most interventions to improve HAART adherence lose effectiveness within weeks of trial conclusion. We therefore propose iHAART (i$), a smartphone application (app) that delivers personalized interventions with content and dose that adapts in real time to variable HAART adherence in stimulant users. The most innovative features of i$ are its adherence interventions. The first type of intervention involves dynamic graphical images derived from real time adherence data that allow participants to monitor the health effects of their own antiretroviral adherence. The second genre of intervention is combinatorial text messages. We will conduct formative qualitative interviews with stimulant users receiving HAART to identify text-based messages s/he personally believes would be effective at promoting adherence for her/himself. We will frame each individual's self-generated text messages in Motivational Enhancement Therapy (MET) and organize them according to potency, the content of message the participant would like to receive to improve upon a current degree of adherence. Then we will dissect messages into dialogue states (eg, greeting, intervention, closing, etc). i$ software will then randomly select one item from each dialogue state and combine them into new text messages that promote HAART adherence. This method allows the automated creation of millions of different adherence interventions. Using these two types of messages, i$ will continually produce fresh HAART adherence interventions to prevent intervention fatigue. We will then assess over a 3 month period the functionality and acceptability of i$ among stimulant (e.g., methamphetamine, cocaine, and MDMA) users receiving HAART. Declining adherence will trigger the more frequent delivery of interventions with greater potency. Improving adherence leads to the less frequent delivery of content that is primarily supportive. The specific aims are: 1) To provide an adaptive, personalized, mobile technology to improve HAART adherence in patients with HIV/AIDS; and 2) To evaluate participant experience with an adaptive, personalized, mobile technology to understand the barriers and facilitators of technology utilization with a specific focus on usability as well as mechanisms of action that might underlie the potential effectiveness of the interventions and quality of the patient-technology relationship. Innovation: i$ will vary the potency of its intervention according to the degree of adherence, a dose-response adaptability has never before been achieved. Significance: i$ uniquely targets long-term maintenance of HAART adherence, a particularly acute problem in the HIV treatment field. Impact: i$ will provide ongoing assessment and individualized feedback to enable powerful new interventions for many common, intractable, and expensive diseases.